A power source device is known which includes, for example, four relays, i.e., first to fourth relays, two secondary batteries, a boost converter in which connection of the two secondary batteries are switched between a series connection state and a parallel connection state relative to an electric load while the voltage applied to the electric load is adjusted by the boost converter (see Patent Document 1).
In addition, a power source device is known which includes, for example, four first to fourth switching devices, two reactors, and two DC power sources in which connection of the two DC power sources are switched between a series connection status and a parallel connection status relative to an electric load while the voltage applied to the electric load is adjusted (see Patent Document 2).